After a massive earthquake struck Port-au-Prince, the world is now getting a sense of the scale of the catastrophe in Haiti. The U.S. military now has several dozen personnel on the ground to assist in the relief effort — but getting people and equipment there presents a serious challenge.

Take, for instance, the main airport. The runway may be intact, but the control tower lost communications after the quake.

Air Force Gen. Douglas Fraser, the four-star chief of U.S. Southern Command, told reporters yesterday the U.S. military was initially “focused on getting command and control and communications there so that we can really get a better understanding of what’s going on.”

It’s not just the airport where connectivity is lost. The headquarters for MINUSTAH, the United Nations Stabilization Mission in Haiti, partially collapsed, and a significant portion of its communications network was severed.

Fraser said the military was adapting its plans as more information emerged. As of yesterday, there were just over 60 U.S. military personnel in Haiti, primarily as part of a military liaison group; another small contingent is supporting the UN Mission. The U.S. Agency for International Development is sending a Disaster Assistance Response Team, and has activated the Fairfax County Urban Search and Rescue team from northern Virginia and a Los Angeles County Search and Rescue Team. Each team includes up to 72 personnel, six search-and-rescue dogs plenty of rescue gear.

Several Coast Guard cutters — pictured above — are already off the coast of Haiti. The aircraft carrier USS Carl Vinson, which was at sea off of Norfolk, Va., is now en route; the Navy plans to stock it with provisions to support relief efforts. Fraser also said the military was considering sending a large-deck amphibious ship with an embarked Marine Expeditionary Unit, which might be better suited for supporting onshore relief operations. That vessel may arrive a few days after the Vinson.

At this point, the human cost is difficult to estimate. UN Secretary-General Ban Ki-moon said in briefing yesterday that “casualties are certain to be heavy.” Of Haiti’s total population of 9 million people, he added, initial reports suggest roughly third may be affected by the disaster.

You can follow some of the latest updates with the #haiti hashtag on Twitter. I’ve also been tracking my friends Jason Maloney and Kira Kay of the Bureau for International Reporting; they were shooting a documentary in Saint Marc, north of Port-au-Prince, when the quake struck. They’ve felt the aftershocks, and write that the logistics of getting into Port-au-Prince are looking pretty rough right now.